1. Field of the Invention
This invention relates to microprocessors. In particular, the invention relates to power management.
2. Description of Related Art
The Advanced Configuration and Power Interface (ACPI) specification introduces a new method for performing platform power management and enumeration. The architecture is table-based and has the capability to execute control methods written in ACPI Source Language (ASL) code. The ASL code is interpreted by the Operating System (OS) and allows the platform to execute actions and notify the OS of certain events. Certain operations in ASL code are prohibited by the OS interpreter. Therefore, in many cases, it is required that the ASL code communicate with the platform System Management Interrupt (SMI) handler to perform actions that would otherwise be blocked by the OS. It is possible for the ASL code to generate SMI""s by writing specific values to the SMI command port in the chipset, which then results in a SMI being generated that can perform specific actions. Arguments and return parameters can then be passed to and from the ASL code in scratchpad registers located in the chipset.
Recently, advances in microprocessor technology offer mobile users two performance modes: Maximum Performance mode and Battery Optimized mode. Maximum Performance mode takes advantage of the additional power provided by an alternating current (AC) power source to provide a new level of mobile personal computer (PC) performance, while Battery Optimized mode provides optimal performance while running on battery. An OS may operate in either of the two modes. In order to force the OS out of the Maximum Performance mode, it is necessary to invoke an ASL method from within a SMI handler.
Therefore, there is a need to have a technique to invoke an ASL method from an interrupt handler.